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Abstract Introduction: Epcoritamab (epco) and glofitamab (glofit) are bispecific antibodies (BsAbs) approved for the treatment of patients (pts) with multiply relapsed or refractory (r/r) large B-cell lymphoma (LBCL). Though response rates are relatively high, most patients (pts) eventually experience progression of disease (POD). We sought to investigate the treatment patterns and clinical outcomes following POD post-BsAb for r/r LBCL Pts, as this has not previously been described. Methods: We performed a multicenter retrospective study including 21 US centers evaluating pts with r/r LBCL receiving commercially available epco or glofit between 2023 and 2025. Baseline characteristics and outcomes were extracted from medical records. Efficacy and survival outcomes were assessed by site investigators and included overall response rate (ORR), complete and partial response (CR, PR) rates, progression-free survival (PFS) and overall survival (OS), analyzed using the Kaplan Meier method. Results: As of May 15, 2025, a total of 312 pts with r/r LBCLs were treated with BsAb, of whom a total of 168 (53.8%) pts experienced POD [104 of 193 (53.8%) treated with prior epco and 64 of 119 (53.8%) treated with prior glofit]. Pts with POD had a median age at BsAb start of 67 years (interquartile range [IQR] 58-76), most were male (68.4%), and the most common histology was diffuse large B-cell lymphoma not otherwise specified (n=122 [71.8%]). Sixty-seven of 168 pts (39.9%) with POD after BsAb had experienced primary refractory disease defined as failure to achieve PR or CR to frontline therapy. A total of 102 (60.7%) pts with POD to BsAb had received chimeric antigen receptor (CAR) T-cell therapy prior to BsAbs, with 33.3% of these pts being refractory to CAR T and 30.4% progressing within 6 months of CAR T-cell infusion. The median time to progression following BsAb start was 48 days. Following POD, 70 pts received no further anti-lymphoma therapy. Among 98 pts receiving subsequent therapy, 85 initially received systemic therapy and 13 initially received local therapy with radiation (concurrently with systemic therapy in 8 pts). The most commonly-used next line of systemic therapies included: loncastuximab tesirine in 19 pts (ORR 16.7%, all PR); commercial CAR T in 11 pts (ORR 50% [CR 36.4%, PR 18.2%); tafasitamab with lenalidomide in 7 (no responses); and other chemotherapy in 46 pts (ORR 27.6% [CR 24.1%]). The median follow-up time from POD was 9.2 months among survivors (95% confidence interval [CI] 7.8-13.3). Among those who initiated subsequent-line therapy following BsAbs, the median progression-free survival (PFS2) was 1.9 months (95% CI 1.5-2.4) and median overall survival (OS) from initiation of subsequent-line therapy was 3.9 months (95% CI 2.4-5.5). The estimated 1-year OS following initiation of next therapy was 12%. Conclusions: We report the outcomes of largest cohort of pts with POD post-BsAbs in r/r LBCL. Progression events occurred early after initiation of single agent BsAbs, and almost half of pts who progressed did not receive subsequent therapy. For those who received standard subsequent-line therapy after POD, response rates and survival outcomes were poor. Pts with POD after BsAB should be strongly considered for clinical trials of novel therapeutics or combination therapies.

Abstract Background Myeloproliferative neoplasms (MPNs) can progress from chronic phase to accelerated or blast phase (MPN-AP/BP), a transition with poor prognosis and limited treatment options. While some abnormalities have been described, the genomic and clonal drivers of transformation remain poorly defined. We characterized mutational and structural alterations in MPN-AP/BP, leveraging paired samples to trace clonal evolution. Methods We profiled 186 samples from 160 individuals, including 159 MPN-AP/BP and 27 chronic-phase MPN samples (26 MF, 1 PV), using targeted sequencing of a 588 gene panel (mean depth: 709x). Paired pre- and post-transformation samples were available for 26 patients (n= 52). A consensus pipeline was used to detect somatic mutations, copy number variations (CNVs), and copy-neutral loss of heterozygosity (cnLOH). Clinical cytogenetic data were integrated when available. Single-cell validation is ongoing. Results Genomic complexity was widespread: 99% of patients harbored ≥1 oncogenic mutation (median 4; range 1–10). In total, 859 mutations were identified, most commonly in JAK2 (68%), ASXL1 (28%), TET2 (26%), SRSF2 (24%), TP53 (22%), and RUNX1 (22%). 684 structural alterations were identified in 86% of patients (median 3; range 1-20), including arm-level (22.5%), segmental (>5 Mb; 60%), and focal (<2 Mb; 9%) alterations. Recurrent events included 9p cnLOH (16%), del(5q) (13%), del(17p) (10%), and focal deletion of 21q22.12 involving RUNX1 (10%). Complex karyotypes (≥3 abnormalities) were observed in 55% of patients. Biallelic mutations accounted for 21% (183/859) of mutations, affecting 58% of patients across 21 genes, most frequently JAK2 V617F (28%), TP53 (17%) and TET2 (14%). Patients with biallelic mutations in these genes had significantly higher blast percentages compared to those with monoallelic mutations (p<0.05), highlighting an association with aggressive disease. In 26 patients with longitudinal samples (chronic phase MPN and MPN-AP/BP), 87% (125/144) of mutations were already detectable during the chronic phase, on average more than 7 years prior to transformation. Only 11% (16/144) of mutations were newly acquired, including additional RUNX1 and TP53 hits, or structural changes that converted pre-existing JAK2 V617F and TP53 R248Q mutations from monoallelic to biallelic via 9p cnLOH or 17p loss, respectively. These findings suggest transformation is often driven by outgrowth of pre-existing high-risk clones, indicating that these clones likely have a competitive advantage and that the mutations within these clones have a cooperative biological interaction which underlies this competitive advantage. To investigate this hypothesis, we examined whether patterns of recurrent co-mutations were identifiable in this cohort. We identified recurrent co-occurring mutations in SRSF2-IDH2, ASXL1-SRSF2, and ASXL1-EZH2, which were enriched at transformation (p < 0.05; Fisher exact test). Importantly, presence of these co-mutations was consistently associated with a higher transformation risk in two independent cohorts of MF patients from Mayo Clinic (n= 405) and University of Florence (n= 518). Clonal architecture analysis revealed that these co-mutations frequently arose within the same malignant clone: 100% for SRSF2-IDH2, 80% for ASXL1-SRSF2, and 85% for ASXL1-EZH2, and are often within the dominant clone. Prior studies have demonstrated mechanistic interplay between SRSF2 and IDH2 (Yoshimi et al.), as well as ASXL1 and SRSF2 (Sui et al.) mutations in myeloid malignancies. We assessed functional synergy of ASXL1-EZH2 using a murine model and identified that dual deletion caused a rapidly fatal myeloid neoplasm with shorter survival than single-gene loss. These results reinforce that functional synergy emerges within a shared cellular context, supporting clonal co-dependence as a driver of progression. Single-cell RNA sequencing of ASXL1-EZH2 mutant cases is ongoing and will be presented. Conclusions Transformation to MPN-AP/BP is driven by gradual clonal remodeling and expansion of pre-existing high-risk abnormalities. Biallelic and multi-hit alterations in TP53, JAK2, TET2, and RUNX1 promote clonal dominance and blast progression. Recurrent co-mutations such as IDH2-SRSF2 and ASXL1-EZH2 arise within the same clone, exhibit functional synergy, and are linked to poor outcomes. These findings support the clinical utility of early clonal and co-mutational profiling to guide risk-adapted intervention.

Abstract Background and Significance: Polycythemia vera (PV) is a myeloproliferative neoplasm associated with pathologic erythrocytosis, most often driven by somatic mutations in the JAK2 gene. A key treatment goal is maintaining hematocrit (HCT) below 45% to reduce thromboembolic complications. Current standard of care for patients diagnosed with PV, including phlebotomy (PHL) and cytoreductive therapies (CRT), can be burdensome, may lead to intolerable adverse effects, and often are associated with symptoms of iron deficiency. DISC-3405 is an investigational, novel, humanized immunoglobulin (Ig)G1 monoclonal antibody that targets transmembrane serine protease 6 (TMPRSS6, also known as matriptase 2) to stimulate endogenous production of hepcidin, a peptide hormone secreted by hepatocytes and the key regulator of iron homeostasis. In a randomized, placebo-controlled study in healthy volunteers (DISC-3405-101), DISC-3405 administered subcutaneously at doses between 37.5-300 mg was well-tolerated, resulted in dose-dependent pharmacokinetic (PK) profiles, significantly increased hepcidin production with corresponding reductions in serum iron levels, and reduced HCT (Liu et al, EHA 2025, PS2207). DISC-3405 is being developed as a potential treatment for patients with PV requiring HCT reduction, regardless of baseline risk or concurrent CRT. Study Design and Methods: This is a multi-center, open-label, 52-week Phase 2 study enrolling up to 20 patients with PV in the United States to assess the safety, tolerability, PK, pharmacodynamics (PD), and therapeutic effect of DISC-3405 on PV disease control as evidenced by HCT reduction and PHL requirements. After an observation period of 4-12 weeks, participants will be treated and followed for 52 weeks and dosed up to 300 mg every 2 weeks. After 52 weeks, participants can continue in an optional 2-year continuation phase where long-term safety and efficacy will continue to be assessed. The main efficacy endpoints of the study include the proportion of participants achieving therapeutic response, defined as absence of PHL eligibility; number of PHLs during the treatment period; and proportion of participants with HCT values <45% throughout the study. PHL eligibility is defined as (1) HCT ≥45% and ≥3% (absolute change) of pre-treatment values or (2) HCT >48%. Eligible participants include adults 18 or older who meet the 2022 World Health Organization diagnostic criteria for PV. Clinically acceptable laboratory values include HCT <45% prior to Day 1 (dosing) or HCT <48% if followed by a PHL within 2 weeks prior to first dose of study drug, white blood cells 4000/μL to 20,000/μL (inclusive), and platelets 100,000/μL to 1,000,000/μL (inclusive). Participants should have at least 3 PHL in 26 weeks or 5 PHL in the 52 weeks prior to screening, and at least 1 PHL within 12 weeks prior to screening. Participants receiving CRT must have been on the therapy for at least 6 months and on a stable PV treatment regimen, including hydroxyurea, interferon, or ruxolitinib, for at least 2 months. Participants treated with only PHL must have stopped CRT 6 months before screening. Key exclusion criteria include participants that require PHL at HCT levels <45%, clinically significant thrombosis within 2 months prior to study treatment, active or chronic bleeding, estimated glomerular filtration rate of <30 mL/min/1.73 m2, and history of invasive malignancies within the last 5 years, except localized cured prostate cancer and cervical cancer, or other malignancies deemed acceptable in discussion with the Sponsor. The study will enroll participants from approximately 15-20 sites in the United States. Additional details can be found at https://clinicaltrials.gov/study/NCT06985147.

Abstract Background Etentamig is a second-generation B-cell maturation antigen (BCMA) x CD3 bispecific antibody that has shown promising efficacy and a favorable safety profile in heavily pretreated patients with relapsed/refractory multiple myeloma (RRMM). Etentamig possesses a unique combination of 2 high-affinity BCMA binding domains, coupled to a low-affinity CD3 binding domain that have been shown to reduce the negative impact of soluble BCMA (sBCMA), decrease risk for cytokine release syndrome (CRS), and drive sustained T-cell activation with reduced immune exhaustion in preclinical models of MM (Blood 2023;142 [suppl 1]:4666). Here, we describe correlative biomarker analyses from Phase 1 (NCT03933735) and Phase 1b (NCT05650632) clinical trials of etentamig in RRMM designed to assess the impact of sBCMA on clinical response and pharmacodynamic changes in proinflammatory cytokines, and T-cell redistribution, activation, proliferation, and exhaustion. Methods Peripheral blood and serum samples from patients with RRMM enrolled in Phase 1 and Phase 1b open-label studies who received etentamig monotherapy were collected at baseline, on treatment, and at disease progression. The Phase 1b study consisted of dose-optimization (DO) and dose-expansion (DE) phases. During DO, patients received a single step-up dose (SUD) of intravenous etentamig (2 or 4 mg) on Cycle (C) 1 Day (D) 1, followed by the target dose of 60 mg on D4. In DE, based on DO findings, patients received the recommended etentamig SUD (2 mg) on C1D1, followed by 60 mg on D4 with modified dexamethasone predosing. Samples were analyzed by flow cytometry for immune cell populations, Luminex® for cytokines, and electrochemiluminescence for sBCMA. Peripheral blood mononuclear cells and bone marrow mononuclear cells (BMMC) at baseline and on-treatment were subjected to single-cell Cellular Indexing of Transcriptomes and Epitopes sequencing (scCITEseq) and single-cell T-cell receptors (scTCR) / B-cell receptors clonality analyses. Results While baseline serum sBCMA levels did not correlate with clinical response to etentamig at the selected dose level of 60 mg every 4 weeks (Q4W) with 2 mg SUD, a reduction in sBCMA levels over time was associated with best International Myeloma Working Group response. Etentamig treatment led to a rapid and transient increase of proinflammatory cytokines and promoted T-cell redistribution, activation, and proliferation. Maximum reduction in peak levels of CRS-related cytokines, including (interleukin [IL]-6, IL-8, IL-10, tumor necrosis factor–a), were observed in DE compared with DO and 60 mg Q4W without SUD. Peak induction levels of proinflammatory cytokines during C1 correlated with occurrence of CRS (≥Grade [G] 1) as well as clinical response across dose levels. A modified dexamethasone premedication schedule of 2 mg/60 mg Q4W cohort for C1 resulted in significantly reduced baseline levels of IL-6 and key macrophage-associated cytokine/chemokines (eg, monocyte chemoattractant protein-1 and macrophage inflammatory protein-3 beta). Incidence of CRS was lowest in the 2 mg/60 mg Q4W cohort (26% G1, 4% G2, 0% ≥G3). Higher T-cell to myeloma cell ratio in BMMCs at baseline correlated with better response to etentamig. scCITEseq and scTCR analysis revealed that at baseline, responders also had greater CD8+ T-cell cytotoxic activities, increased TCR clonality, and elevated inflammatory signatures in T-cells from both peripheral blood and bone marrow. Etentamig at a dosage of 60 mg Q4W resulted in significant clonal expansion of CD8+ effector T-cells and enhanced gene expression signatures related to activation and cytotoxicity in both CD8+ T effector and natural killer cells. Along treatment cycles, responders maintained their T-cell fitness, high clonality, and low T-cell exhaustion levels. Frequency of baseline CD4+ or CD8+ T-cell exhaustion (programmed cell death receptor 1+/ T cell immunoglobulin and mucin-domain containing-3 +) did not impact clinical response at optimal dose level of 2 mg/60 mg Q4W etentamig. Conclusions Responses to etentamig were independent of baseline sBCMA levels and resulted in rapid and transient proinflammatory cytokine production that promoted robust T-cell redistribution, activation, and proliferation indicating that the optimal dose of etentamig (2 mg/60 mg Q4W) maximizes its clinical potential as a convenient, safe, and effective therapy for MM.

Abstract Background: Venetoclax (VEN)+obinutuzumab (VO) is an effective therapy for CLL/SLL requiring regular monitoring for tumor lysis syndrome (TLS) during VEN ramp-up. The CLL14 trial of VO reported no TLS during VEN ramp-up; however, there are limited real-world data on monitoring practices and TLS outcomes for different dose levels and monitoring timepoints. This study assessed VEN initiation prophylaxis and monitoring outcomes for patients (pts) with CLL/SLL starting VO in first line (1L) in an outpatient, real-world setting. Methods This interim analysis relied onretrospective observational data from 4 US sites of the CLL Collaborative Study of Real-World Evidence (CORE). Adult pts with CLL/SLL were eligible if they: (1) started VO per-label outside of a clinical trial in 1L, or immediately after exposure in 1L to agents with different mechanisms of action (i.e., BTKi, anti-CD20 only) of <30 days; (2) prior to VEN start, had either (i) low physician-determined tumor burden (TB) (i.e., all lymph nodes [LN] <5 cm and ALC <25 x 109/L), or (ii) medium physician-determined TB (i.e., any LN ≥5-<10 cm or ALC ≥25 x 109/L) with creatinine clearance ≥80 mL/min; (3) had no strong CYP3A inhibitors or prophylactic rasburicase from 3 days prior to VEN start until end of VEN ramp-up; and (4) had VEN ramp-up in an outpatient setting. TB-related labs/imaging was assessed from 2 months prior to obinutuzumab initiation (i.e., index date) until VEN start. VEN characteristics (i.e., dosing, duration), prophylaxis measures (i.e., antihyperuricemics and IV hydration), and TLS-related monitoring and management (i.e., lab results and interventions received) were collected per ramp-up week and TLS monitoring timepoint. Results Of 128 pts in CORE who initiated VO in any line, 72 pts met inclusion criteria (low TB: 57 [79.2%]; medium TB: 15 [20.8%]). Median (IQR) age was 62 (56.0, 68.5) years, 58.3% were male, and 81.9% had ECOG grade ≤1. Among pts tested, 7/68 (10.3%) had del(17p)/TP53 mutation and 43/66 (65.2%) had unmutated IGHV. Median (IQR) time from index to VEN start was 23.0 (22.0, 30.0) days. Most pts completed ramp-up (98.6% [71/72]) and followed a per-label regular dosing schedule (93.1% [67/72]). Prior to VEN ramp-up, all pts received prophylactic antihyperuricemics (allopurinol: 71 [98.6%]; febuxostat: 2 [2.8%]) and prophylactic hydration. In the 2 days prior to a dose escalation for at least 1 week of ramp-up, prophylactic IV hydration was reported for 27 (37.5%) pts based on physician determination. One pt stopped VEN after week 2 due to neutropenia (grade 3+). During ramp-up (median [IQR] of 9 [8, 12] blood tests per pt), no lab or clinical TLS was reported. Of 21 (29.2%) pts who received an intervention following a lab assessment, most had low TB at VEN start (16 [76.2%]). All interventions were either prophylactic or non-TLS-related. Following a lab assessment for at least 1 week of ramp-up, prophylactic IV or escalated oral hydration intervention was reported in 17/21 pts (81.0%) based on physician determination (e.g., to manage impaired baseline renal function in those with low TB, patient request, or institutional practice) (IV hydration: 15 pts; escalated oral hydration: 2 pts). By per-label monitoring timepoints, hydration intervention was given prophylactically following pre-dose lab tests for 7 pts (across weeks 1-5), 6-8 hours post-dose for 5 pts (weeks 1-2), and 24 hours post-dose for 10 pts (weeks 1-2). By per-label monitoring timepoints, other non-TLS-related interventions (i.e., blood transfusion for anemia, insulin for hyperglycemia, and potassium for non-TLS-related hypokalemia) were given following pre-dose lab tests for 2 pts (weeks 1-5) and 24 hours post-dose for 4 pts (weeks 1-2). Conclusion Consistent with the CLL14 trial, no TLS was reported in this real-world, interim analysis of pts with mostly low TB and good renal function at 1L VO initation. All interventions during VEN ramp-up were prophylactic or non-TLS-related, with prophylactic hydration commonly given based on physician preference. These results suggest that VO initiation is manageable in an outpatient setting. Consideration should be given for simplified monitoring requirements including potential removal of 6-8 hour post-dose lab in this population and be further explored in prospective studies. Data collection for this study is ongoing to further contextualize real-world VEN initiation prophylaxis and monitoring outcomes in a larger cohort.

Abstract Introduction: Graft Failure (GF) is a rare but devastating outcome of HCT. Primary GF (PGF), defined as a failure of neutrophil recovery by Day+28, is straightforward to diagnose. Diagnosing secondary GF (SGF) is more challenging, with its broad time-range, multiple confounding diagnoses, and lack of predictive biomarkers. In BMT CTN1703/1801, we analyzed patients receiving RIC HCT for heme malignancies with either Tac/MTX (n=159) or PT-Cy (n=165) GVHD prophylaxis. SGF was defined as donor chimerism <5% after initial donor engraftment. With Tac/MTX, there were 3 PGF and 1 SGF diagnoses. With PT-Cy, there were 4 PGF and 6 SGF. Median SGF diagnosis was Day +64 (range: Day+28-215). There were too few Tac/MTX patients to analyze SGF, but sufficient events with PT-Cy. To identify PT-Cy SGF predictors, we leveraged lymphocyte, T, B, and NK cell reconstitution analysis. In SGF we found an early, profound deficit in the reconstitution of all major lymphocyte populations, including total lymphocytes, T, B, and NK cells, as early as Day+28. This enabled the modeling of a SGF risk classifier based on the Absolute Lymphocyte Count (ALC). Methods: Clinical ALC measurements were performed on all SGF patients (n=6) and on non-GF controls with ALCs available (146 of 155 non-GF patients). Flow cytometry was performed on all PT-Cy SGF patients (n = 6) and from a subset of non-GF controls (n = 18: controls were chosen as patients without relapse or severe GVHD, to reduce confounders introduced by immunologic interventions, and for whom all samples, including from the graft infusion, were available). T, B, and NK counts, as well as T cell subsets, were compared (using Welch's T test) on Days 7, 14, 21, 28, 42, 63, 98, 180, 270, 365, 730, with SGF patients censored on the day of GF diagnosis. To interrogate the optimal ALC cutoff, the cumulative incidence of SGF was computed at Days +28 and +42, with death without GF as a competing risk. Results: We have previously demonstrated that, compared to Tac/MTX, PT-Cy patients exhibited an early decrease in reconstitution of all T cell populations (with normal NK and B cell reconstitution). Here we focused specifically on PT-Cy patients with or without SGF. Graft CD34 counts/kg were not different between SGF patients and non-GF patients (mean CD34/kg = 1.38 x10e6 (SGF) vs 0.67 x10e6 (non-GF, p = 0.61) However, even amidst the overarching early suppression in T cell reconstitution with PT-Cy, SGF patients could be easily distinguished from the larger PT-Cy cohort, based on more profound deficits in ALC, T, B and NK cells reconstitution, measured using 2 strategies: (1) SGF patients demonstrated significant early (Day +28) quantitative defects in the reconstitution of the ALC (mean +/- SEM 262+/-32 cells/µL (non-GF) vs 60 +/- 25 (SGF, p<0.0001), CD4 T cells (62 +/- 12 cells/µL vs 19+/-15, p=0.048), CD8 T cells (15 +/-3 cells/µL vs 3.5 +/-1 p=0.0009), all CD8 T cell subpopulations, as well as NK cells (116+/-31 cells/µL vs 2.9+/-1.4 cells/µL, p= 0.002) and B cells (3.5 +/-1.4 cells/µL vs 0.16+/-0.07 p =0.03). (2) In SGF, there was a significant deficit in the rate of rise of all major lymphocyte populations between Days 28-42-60 vs non-GF, including CD4 T cells (p<0.0001), CD8 T cells (p = 0.0002), B cells (p<0.0001), and NK cells (p =0.048). These discoveries suggested that a classifier could be identified to risk-stratify patients for SGF. We explored an ALC cutpoint, amenable to standard clinical lab analysis. A statistically significant threshold was identified at both Days+28 and +42, with Day+42 being most predictive: A threshold of 120 cells/µL was identified as optimal, with landmark analysis documenting a SGF rate of 34.7% below the cutpoint, and SGF of 1% above it (HR = 45.9, 95% CI 5.7 - 366). Conclusions: Despite the small number of events, PT-Cy patients with SGF demonstrated a distinctive reconstitution trajectory that encompassed an early, substantial, and sustained deficit in all lymphocyte counts, as well as a lack of their longitudinal expansion. This enabled the discovery of a candidate ALC biomarker cutpoint at Day+42 that could distinguish patients who were more likely to develop SGF. If confirmed, these data could generate a predictive biomarker for SGF, which would enable the design of trials evaluating early interventions (e.g. CD34+ boosts, DLI, modification of immunosuppression) to improve outcomes for these patients.

Abstract Background: Dissemination and implementation science (D+I) efforts often begin after clinical trial (CT) efficacy data are available. However, delaying this work limits opportunities to identify barriers and facilitators that can enhance adoption of evidence-based practices. Integrating D+I during trial development, activation, and conduct supports more timely, effective, and scalable implementation. The Blood and Marrow Transplant Clinical Trials Network (BMT CTN) includes >125 centers, conducting transplant and cellular therapy (TCT) trials with practice-changing potential, with >17,000 patients enrolled since 2001. Data from Center for International Blood and Marrow Transplant Research (CIBMTR) provides a way to measure real-world adoption. With this comprehensive structure in place, the BMT CTN launched a D+I Committee that established a D+I process to better understand uptake of CT findings and to leverage that information to promote adoption. Methods: Informed by established D+I frameworks, a structured, cyclical process to integrate implementation considerations spanning the CT lifecycle was developed. A multidisciplinary team including experts in D+I, clinicians, and investigators iteratively refined the proposed D+I algorithm. The process begins upstream when a trial concept is approved to move forward, it is shared with the D+I Committee for initial assessment. This includes a landscape review for studies in development using CIBMTR data, literature, and expert experience. The Committee then reviews the developing protocol with the BMT CTN protocol team to proactively identify implementation barriers and facilitators to implementation in real-world settings and outline plans for dissemination. The Committee also provides recommendations for integrating relevant implementation data collection and analyses within the protocol. After study completion, both clinical efficacy and implementation outcomes are analyzed, followed by active dissemination. Additional assessment using surveys, qualitative methods, and CIBMTR data occurs after dissemination to understand adoption. Insights gathered also inform further refinement of the process. Tools and templates are in development to build capacity and ensure consistency for Committee members. Results: To date, the Committee has published three peer-reviewed articles addressing implementation implications of three BMT CTN trials (PMC7735536, PMC8578257, PMC9364468) and a fourth is in press. Using the designed D+I process flow, a current effort used a survey sent to US CIBMTR centers, to evaluate factors influencing the implementation of results of the BMT CTN 1703 trial of post-transplant cyclophosphamide as graft-versus-host disease (GvHD) prophylaxis and assessed dissemination and adoption considerations for the upcoming BMT CTN 2203 CT of ruxolitinib as GvHD prophylaxis. CIBMTR data is being analyzed to demonstrate practice patterns before, during, and after BMT CTN 1703 study completion. This effort has allowed for further refinement of the BMT CTN D+I process flow and has highlighted critical opportunities for incorporating dissemination and implementation objectives and endpoints into BMT CTN protocols. We also used the process to guide a review of severe aplastic anemia treatment gaps and ongoing studies. This review underscored how proactive transplant and non-transplant stakeholder engagement and early implementation planning, core elements of this process, can bridge evidence to practice and advance access to care. A complementary survey on current practice patterns in severe aplastic anemia is ongoing. Conclusions: With the existing structure of the BMT CTN and associated practice registry of the CIBMTR, the BMT CTN D+I Committee developed a systematic process to build D+I considerations into trial workflows to increase real-world impact. This process aims to ensure that barriers to uptake of trial results can be identified and addressed appropriately, improving care quality for patients undergoing TCT.

Abstract Background: Prolonged cytopenias are a well-recognized complication following CAR-T therapy, leading to increased morbidity and healthcare utilization. Autologous SCB offers a potential strategy to promote hematologic recovery. We conducted a retrospective multi-institutional analysis across 18 centers comparing outcomes of SCB versus supportive care alone in RRMM patients who experienced prolonged cytopenias >30 days after CAR-T infusion. Methods: Patients were included if they received SCB within 1 year after commercial CAR-T between 6/2021 and 3/2024. To identify matched controls, we reviewed other CAR-T recipients from the same consortium and selected those with an absolute neutrophil count (ANC) of <0.72x109/L and platelet count of <21K at day 30 post-infusion-thresholds representing the 75th percentile of cytopenia severity in the SCB cohort. These criteria ensured control patients had comparable hematologic toxicity but without SCB. Hematologic recovery in the SCB cohort was assessed using the CIBMTR engraftment criteria. For the non-SCB (nSCB) group, cell counts were analyzed cross-sectionally at day 90 post-CAR-T and compared to the SCB cohort with Kruskal Wallis tests. Progression-free survival (PFS) and overall survival (OS) were evaluated using Kaplan Meier methods. Results: Of the 590 CAR-T recipients, 91 patients (15.4%) developed prolonged cytopenias; 39 patients received SCB and 52 did not. SCB patients more frequently had ISS stage III disease (23.1% vs. 11.5%), exrtamedullary disease (59% vs. 46.2%) and penta-refractory status (43.6% vs. 34.6%). The median number of prior lines of therapy was 6 in both cohorts. Thirteen patients (33.3%) in the SCB and 11 (21.2%) in the nSCB received high intensity infusional chemotherapy (DCEP/PACE/HyperCVAD). Pre-CAR-T cytopenias tended to be less frequent in the SCB vs. nSCB cohort: ANC <1000 in 5.1% vs. 13.5%, Hgb <8 in 23.1% vs. 21.2%, and platelets <50K in 28.2% vs. 40.4%. Median plasmacytosis in the bone marrow prior to CAR-T in the SCB group was 35% and 47.5% in the nSCB group. In the SCB cohort, 2 patients harbored DNMT3A mutations, one of whom had CCUS. Ide-cel was administered in 64.8% and cilta-cel in 35.2% of all patients. The rates and grades of cytokine release syndrome did not differ between groups. Six patients (15.4%) had HLH in the SCB group vs. none in the control group. All (100%) SCB patients received growth factor support; 58% also received TPO agonists. In the nSCB group, 43 patients (82.7%) received growth factor, and 16 patients (30.8%) received TPO agonists. Out of 24 pre-SCB bone marrow biopsies available, only 1 patient had relapsed MM while the remainder had hypocellular marrows. Median CD34+ cell dose was 2.93 million/kg (range: 1.76-23.55) administered at a median of 53 days post-CAR-T (range 24-265). All but one patient (97.4%) in the SCB group achieved hematologic recovery; median time to recovery was 24 days (range 9-87). No new toxicities attributable to SCB were observed. On day 90 post CAR-T infusion, SCB patients had higher median ANC (2.12 vs. 1.59x109/L, p=0.277), Hgb (10.6 vs. 8.7g/dL, p=0.002), and platelet counts (135 vs. 35K/L (p<0.001). Minimal residual disease negativity was achieved in 82.4% (SCB) vs. 83.3% (nSCB). Infections occured in 53.8% and 48.1% of SCB and nSCB cohorts. All serious infections occurred prior to SCB. There were 12 deaths in the SCB group (7 from disease progression, 2 from infection, 1 from neurotoxicity (NT), and 1 unknown) and 27 in the nSCB group (22 from progression, 3 from infection, 1 from HLH, 1 from NT). After a median follow-up period of 12.6 months in the SCB cohort and 11.6 months in the nSCB arm, the mPFS was 11.0 months and 8.2 months, respectively. The mPFS was 10.6 months (SCB) and 5.8 months (nSCB) (p=0.216), and 11.0 months (SCB) and 10.9 months (nSCB), for ide-cel and cilta-cel treated-patients, respectively. Median OS was not reached vs.12.3 months in the SCB vs. nSCB groups, respectively. Conclusion: Overall, SCB was safe and effective in promoting rapid hematologic recovery in nearly all patients. Compared to controls, SCB recipeints had significantly higher Hgb and platelet levels by day 90 post-CAR-T infusion. SCB was associated wih a near doubling of PFS in patients who received ide-cel, though interpretation is limited by non-randomized design and small sample size. Further study is needed to optimize paient selection, timing, and integration of SCB into CAR-T care.

Abstract Introduction: Ciltacabtagene autoleucel (cilta-cel) has shown high efficacy in relapsed MM, but further efforts are needed to mitigate non-ICANS delayed neurotoxicity (DNT) and non-relapse mortality (NRM). Identifying risk factors associated with DNT and NRM may help with risk mitigation by aiding the development of interventions for potentially modifiable risk factors and also help with clinical decision making. Methods: In this multi-center retrospective study from the US MM Immunotherapy Consortium, we evaluated 761 patients treated at 15 centers receiving standard of care cilta-cel for relapsed MM between May 2022 to December 2024. Risk factors for DNT, particularly Parkinsonism and NRM were evaluated in by univariable and multivariable analysis. Any NRM events occurring after disease progression were censored for NRM evaluation. Results: The median age of the cohort was 65 years old (range: 30-88), median prior lines of therapy (pLoT) were 5 (range: 1-23). Cilta-cel was used in earlier relapse (1-3 pLOT) in 16% (n=120) patients. High-risk cytogenetics [del 17p, t(14;16) or t(4;14)] were present in 39%, with extramedullary disease (EMD) in 27% and R-ISS stage III in 18% of patients, respectively. Majority of patients (86%) received bridging therapy with response to bridging (≥ partial response, PR) seen in 33% of patients, respectively. Median follow up was 10.1 months, with response rate of 92% and CR rate of 70%. DNT was seen in 10% (n=75) of patients, with distribution as follows: Parkinsonism in 2.9% (n=22), cranial nerve palsy in 4.6% (n=35) and other DNT in 2.4% (n=18), with some patients manifesting more than one type of DNT. Risk of DNT was higher in patients who did not respond to bridging therapy (Any DNT: 12% vs 6%; Parkinsonism: 5% vs 0.5%, both p<0.05) Of the 22 cases of Parkinsonism, 21 patients (95%) did not respond to bridging, even though they achieved a post CAR-T response with ORR of 91% and ≥ CR in 68%. Absolute lymphocyte count (ALC), a surrogate measure of CAR expansion was higher in patients who developed DNT, particularly Parkinsonism, including ALC at days 7,14,21,28 and as peak ALC in the first month post cilta-cel (p<0.05 for all). Median peak ALC for patients with vs without Parkinsonism was: 5.88 vs 1.17/uL (p<0.001). We evaluated risk of Parkinsonism with various thresholds of peak ALC expansion. Amongst patients who developed Parkinsonism vs. not, peak ALC was as follows, > 1000/uL: 100% vs 57%, > 2500/uL: 73% vs 19% and > 3000/uL: 68% vs 14% (all p<0.001). The absolute risk of Parkinsonism with ALC > 3000 vs ≤ 3000/uL was 12% vs 1%, p<0.001; for ALC 2500 vs ≤ 2500uL was 9% vs 1%, p<0.001. On multivariable analysis, peak ALC > 3000/uL (OR: 12.7, p<0.001) and non-response to bridging therapy (OR: 9.9, p=0.03) were independent risk factors for developing Parkinsonism after cilta-cel. After cilta-cel, 1 and 2 year NRM estimates were 9% and 10%, respectively. Amongst 63 (8%) patients experiencing NRM events, the most common cause of NRM was infectious complications (35, 56%), followed by acute immune-mediated adverse events (AEs) like CRS, ICANS, IEC-HS in 14 (22%), delayed immune mediated AEs like DNT and colitis in 6 (9.5%), second cancers in 5 (8%) and other causes in 3 (5%) patients, respectively. When evaluating the timing of NRM events, the risk of infection related mortality remained relatively stable in the first year, though immune mediated toxicty deaths were uncommon after 6 months, while SPMs were uncommon within the first 6 months. On multivariable analysis, non-response to bridging (HR 2.41, p=0.046), poor performance status ≥ 2, high-risk cytogenetics and age ≥ 70 years were independent predictors for NRM. Conclusion: In a large cohort of over 750 patients receiving cilta-cel, we identified potentially modifiable risk factors for Parkinsonism and NRM. Non-response to bridging therapy and peak ALC > 3000/uL were independent predictors of developing Parkinsonism. Peak ALC of > 2500/uL and > 3000/uL were associated with 9% and 12% absolute risk of Parkinsonism. This indicates that peak ALC of 2500/uL or 3000/uL in the first month after cilta-cel may be a potential biomarker to identify patients for pre-emptive interventions such as steroids that can suppress rapid CAR expansion and perhaps decrease the risk of Parkinsonism. In addition, we need to focus on effective bridging strategies to further decrease the risk of Parkinsonism, as well as NRM with cilta-cel.

Abstract Background: In R/R DLBCL/FL, T-cell engager therapy (TCET) using chimeric antigen receptor T-cell therapy (CART) or bispecific antibodies (BsAbs) are promising options. Patients (pts) with R/R disease post TCET experience dismal outcomes with overall survival (OS)< 5 months (mos). Lonca, an antibody drug conjugate (ADC) targeting CD19 (FDA approved for R/R DLBCL and beneficial in R/R FL) has been increasingly used post-TCET. RWDA of Lonca is limited, especially regarding: 1) impact of CD19 expression on activity, 2) adverse events (AEs) in non-clinical trial setting, and 3) impact of sequencing Lonca and TCET. Thus, we conducted a RWDA of Lonca efficacy and toxicity in R/R DLBCL and FL pre- and post-TCET. Methods: We conducted a multicenter retrospective study of R/R DLBCL or FL pts ≥18 years who received Lonca from 2017 to 2025 at 10 US academic sites. Demographic, pathological, treatment, and AEs were collected. Efficacy outcomes included overall response rate (ORR), complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD). Progression-free survival (PFS) and OS were analyzed by Kaplan-Meier method. CD19 expression by immunohistochemistry (IHC) and/or flow cytometry (FC) prior to Lonca administration was correlated to outcomes. Results: Among 120 pts (DLBCL n= 101, FL n=19), all but 2 pts received Lonca monotherapy. At a median follow-up of 6.1 mos, median PFS and OS were 2.6 mos and 6.7 mos, respectively for the entire cohort. For DLBCL, median age was 66 years (18-89). Median prior lines of therapy (LOT) were 4 (1-11). ORR was 37.7% (CR: 17%, PR: 20.7%), SD: 6%, and PD: 56%. Median PFS was 2.1 mos, and median OS was 5.8 mos. For FL, median age was 62 years (28-88). Median prior LOT was 6 (2-8). ORR was 49.4% (CR: 28%, PR: 21.4%), SD: 14%, and PD: 35.7%. Median PFS was 6.7 mos, and median OS was 6.8 mos. OS by best response (entire cohort) was 11.3 mos and 11.8 mos in those who had CR and PR, respectively, 10.6 mos in SD and 3.5 mos in those with PD. Lonca LOT (2nd-12th line) was not associated with improved OS (p=0.58). Bulky disease (>7.5 cm) was not associated with worse OS (p=0.07). PD to Lonca was associated with PD at 2nd line treatment (OR: 4.3; 95% CI: 1.7–10.9) and 3rd-line treatment (OR: 4.2; 95% CI: 1.5–11.5), elevated lactate dehydrogenase (OR: 1.9; 95% CI: 1.2–2.9), and each subsequent increase of extranodal sites >1 prior to Lonca (OR: 1.5; 95% CI: 1.04–2.1). Among pts with available CD19 status prior to Lonca administration, 28 were FC-positive and 22 were IHC-positive. Of the CD19 FC-positive pts (n=23), 22% (5/23) achieved CR, 26% (6/23) had PR, 8% (2/23) had SD, and 43% (10/23) developed PD. Of the CD19 IHC-positive pts (n=20): 15% (3/20) achieved CR, 20% (4/20) had PR, 5% (1/20) had SD, and 60% (12/20) developed PD. Among all CD19-negative pts (n=7), two achieved CR, one had SD, and four with PD. Any grade AE was seen in 84% of pts. Any grade ≥3 (G3) AE was seen in 62% of pts. Notable G3 AEs included: anemia (35%), lymphopenia (34%), neutropenia (21.6%), thrombocytopenia (20%), infection (17%), fatigue (9%), peripheral edema (5%), pleural effusion (4%), photosensitivity (2.5%), and pruritus (2.5%). Treatment discontinuation due to AEs occurred in 17% (n=21) of pts. Fifty-five pts (50 DLBCL, 5 FL) received both Lonca and CD19 directed CART (Pre-Lonca n=54; Post-Lonca n=1). There was no significant difference in PFS or OS between pts who received CART and those who did not (PFS: 2.7 mos vs 3 mos; OS: 7.4 mos vs 5 mos). BsAb was used in 41 pts (34 DLBCL, 7 FL) (Pre-Lonca n=30; Post-Lonca n=11). No significant difference in PFS or OS was observed between pts who received BsAb pre- or post-Lonca. There was also no significant difference in PFS between pts who received a BsAb (2.2 mos) and those who did not (2.9 mos), nor in OS.Conclusion: In this large RWDA of Lonca, pts who achieved any form of clinical response experienced a significantly longer OS than previously reported for heavily pre-treated pts. Lonca was predominantly administered after TCET; however, there was no significant difference in efficacy between pts who received CART and BsAbs and those who did not. CD19 positivity and earlier utilization of Lonca did not appear to have an impact on response rates. Our findings support a role for Lonca in the treatment of R/R DLBCL pts not candidates for TCET. This RWDA highlights the need to further investigate the sequencing of Lonca in R/R DLBCL and FL.